MEASUREMENT SYSTEM OF LOW FREQUENCY RANGE INTERFERENCE IN LOW-VOLTAGE POWER SUPPLY 50 Hz

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1 Vinna, AUSTRIA, 000, Sptbr 5-8 MEASUREMET SYSTEM OF LOW FREQUECY RAGE ITERFERECE I LOW-VOLTAGE POWER SUPPLY 50 Hz B. Palczyñska, L. Spiralski and A. Konczakowska Gdynia Mariti Acady, ul. Morska 83, 8-5 Gdynia, Poland Tchnical Univrsity of Gdañsk, ul. arutowicza /, Gdañsk, Poland Abstract: Th following papr is a prsntation of th digital syst usd for asuring intrfrnc in low frquncy rang that occurs in low-voltag powr supply. It discusss how th hardwar of th syst, controlld by graphical prograing nvironnt LabVIEW v.4.0 ational Instrunt, has bn ralisd. Furthror, it prsnts basic functions, which th virtual part of th syst prfors. Th papr givs spcial attntion to th thods usd in dtrining quantitis, which dscrib dtrinistic as wll as stochastic typs of intrfrnc. Additionally, th papr dfins th conditions dciding about inaccuracis of th valuation of stiators. Kywords: intrfrnc, virtual instrunt, asurnt of lctrical quantitis ITRODUCTIO By swapping particular parts of hardwar with th blocks of signal procssing and analysis of digital data, on can achiv ffctiv dcras in inaccuracis in th valuation of stiators of th asurd quantitis that dscrib intrfrnc. In th prsntd syst, th acquisition of asuring digital data is prford in accordanc with th rquirnts accptd in dfining factors, paratrs and charactristics of intrfrnc in low frquncy rang in low-voltag powr supply. Softwar of th asurnt syst allows ultipl rptitions of calculation procdurs as wll as odification and altring procssing algoriths. This is ssntial for th analysis of intrfrnc in vry low frquncy rang, whr dtrining stiators rquirs th signal obsrvation ti ranging fro hours to days. But th digital signal procssing dpnds clusivly on th spd of th procssor locatd in th softwar part of th syst. Analogu-digital convrsion is prford at high rsolution, bcaus of th uch lowr lvl of intrfrnc as copard with 50 Hz frquncy signal. Cut-off frquncy of th analogu antialiasing filtrs usd in th hardwar part of th syst changs according to th analysd frquncy band. Such a solution nabls us to analys, with coparabl inaccuracy, intrfrnc in any frquncy dcads []. DESCRIPTIO OF THE SYSTEM Th asurnt syst contains two ain parts (Figur ): th hardwar part (data acquisition block) and th virtual part (consisting of signal procssing and analysing block and graphic intrfac block). Th hardwar part is rsponsibl for convrting th quantitis of th asurd wavfor []. This involvs proportional dcras of all th quantitis of th wavfor without changing its shap. Th ai is to atch th asurd signal lvl with th input of optoisolation aplifirs - th aplifirs sparat high voltag signal. Th initial conditioning follows and is ralisd through th low-pass filtr odul (antialiasing). Th foration of th output digital signal fro th analogu signal taks plac in th A/D convrtr with 6-bit rsolution and sapling rat up to 0 ks/s. Using thr channls at th sa ti allows th aiu sapling rat of 6,6 ks/s. This nsurs th asurnt of intrfrnc in th frquncy band up to, khz. Th frquncy of analysd intrfrnc was liitd by th frquncy of cutting-off antialiasing filtrs. Th dynaics (DR) of 6-bit A/D convrtr is: n DR 0 log 6,0n 96,3 db () whr n6 is th nubr of convrtr bits. Th chang of ral valus of th analogous cours on th convrtr input with th us of th appropriat quantisation lvls lads to rrors. In cas of idal convrsion th rror will b stady in

2 Vinna, AUSTRIA, 000, Sptbr 5-8 Hardwar PC Softwar graphical prograing nvironnt LabVIEW LOW- VOLTAGE POWER SUPPLY DATA ACQUISITIO BLOCK - prliinary conditioning of signal (atching th input signal, isolation of highvoltag signal) - low-pass filtring (antialiasing) - A/D convrsion SIGAL PROCESSIG AD AALYSIG BLOCK virtual instrunts prforing th functions of th standard intrfrnc analysrs GRAPHICAL ITERFACE BLOCK - controlling - onitoring - display Figur. Block diagra of th digital asuring syst of intrfrnc in low frquncy rang th rang (-Q/, Q/) with th standard dviation (Q /) (whr Q is th quantisation rang). Thus, quantisation can b rgardd as qual to th su-up of input cours (t) with th indpndnt nois n(t). Thn, th prcntag proportion of ffctiv quantisation nois n to th rs valu of th wavfor on th quantisd input ay b rgardd as th quantisation rror: n n () Th paratrs connctd with th accuracy card for th input voltag rang +0V ar prsntd in th tabl. Tabl. Th accuracy of asurnt card PCI-MIO-6XE-50 ational Instrunts [5]. Absolut accuracy Rlativ accuracy % of rading offst ois+quantization [µv] drift tp. rsolution [µv] 4 Hrs. 90 days yar [µv] singl pt. avragd [%/ o C] singl pt. avragd 0,0058 0, ,0 397, 56,4 45,8 0,000 60,7 60,3 Th us of th 6-bit rsolution card for th signal on input of th asurnt syst of a fw hundrds V nsurs th accuracy of th syst on th lvl of svral dozns V. Tabl prsnts th asurd noiss lvl of th asuring procss for thr channls. Tabl. Th noiss lvl of asuring procss in bandwidth 0-, khz. o channl DC offst [V] V rs [µv] Th asurd constant coponnt (DC offst) rsults fro th prsnc of offsts brought about by th isolating aplifirs in th st of prliinary conditioning of th syst.

3 Vinna, AUSTRIA, 000, Sptbr THE EVALUATIO OF IACCURACY OF AALYSED ITERFERECE Th virtual part of th syst is ralisd in graphical prograing nvironnt LabVIEW v.4.0 [6]. Signal procssing and analysing block is rsponsibl for prforing functions of th standard intrfrnc asuring instrunts and stochastic analysr. Th sapld signal is procssd in svral virtual instrunts, which ar includd in th ain application as sub-vis. Th softwar contains also th algoriths nabling th valuation of inaccuracy of dtrind stiators dpnding on th obsrvation ti of th asurd signal, linar rang of th asurnt syst and frquncy rquirnts of th syst (Fig. ). Intrfrnc ar analysd in th following virtual instrunts: - THD.vi, which calculats total haronic distortion THD, haronic ratio (prssd as a prcntag of th ratio of th rs valu of a haronic coponnt of ordr n to th rs valu of th fundantal coponnt of th sa wav). - Flickr.vi, which dtrins th valu of short-tr P st and th long-tr P lt flickr svrity [3]. - Stochast.vi, which valuats stiators of an squar (root-an squar) valus, probability dnsity function, probability distribution function taking instantanous valus, intrfrnc powr spctral dnsity, corrlation function). - Off-linJTFA.vi, which prfors joint ti - frquncy analysis. CODITIOS DECIDIG ABOUT IACCURACY OF MEASUREMET OF ITERFERECE I LOW FREQUECY RAGE Frquncy of analysing intrfrnc (f in...f a ) Obsrvation ti of asurd intrfrnc Dynaics of asurnt syst f frquncy rsolution (distanc btwn spctru lins) Avraging ti (nubr of indpndnt sapls) Rsolution of convrtr AD (liiting lvl) Figur. Basic conditions dciding about asurnt inaccuracy of intrfrnc in low frquncy rang. Th frquncy analysis was ad with th us of FFT for th ti fra of r 048 sapls. Th data wr ultiplid by Hanna window function. Th us of th ti window causs FTT rsolution to bco wors (th rlativ bandwidth incrass about,5 tis). Bcaus of th ncssity to dcras th spctru stiation rrors (tab. 3), th calculatd Fourir transfors copl coponnts wr avragd with th us of sction avraging thod (q0). In th analysis of stochastic paratrs connctd with th an valu and th an squar valu, th statistic rror of ths valus asurnt dpnds on th indpndnt nubr of sapls (tab. 3). 4 EXEMPLARY RESULTS OF ITERFERECE AALYSIS Th asurnt syst was usd for acquisition of asurnt data in th ship switchboard of low voltag of frquncy 50 Hz. Rsarch was carrid out on two diffrnt ships: ro-ro and frry. Each ship containd thr phas, thr wir ship lctrical powr systs. Th sourcs of lctrical powr wr thr-phas synchronic gnrators drivn by auiliary cobustion ngins disl powrd. Additionally, shaft gnrators wr usd; thy wr drivn by th propllr shaft of th ain ngin. Th charactristic fatur of th lctrical powr ntworks of low voltag usd on ships is that thr ust b two paralll lctricity gnrating sts working during th ship s anouvring and rloading oprations whn thr is an incrasd dand for lctrical powr. Th lctrical powr of a ro-ro typ ship consists of two frstanding gnrators of 000 kva ach and two shaft gnrators of 500 kva ach. Th noinal voltag on bus bars of th ain switchboard was 400 V. th ain diffrnc btwn th ro-ro and frry lctrical powr systs has bn th nubr of frstanding gnrators. Th frry was quippd with thr gnrators of this kind of 400 kva ach. Thr wr also two shaft gnrators of 375 kva ach. Th noinal voltag on bus bars of ain switchboard was 380 V.

4 Vinna, AUSTRIA, 000, Sptbr 5-8 Tabl 3. Th rlativ standard rrors of stiating of an, an squar valu and powr spctral dnsity. Th rlativ standard rror Estiator corrlatd sapls noncorrlatd sapls τ<<h an valu: G k ~ ( ih) k i an squar valu: ~ ( ih) * i 0 powr spctral dnsity: [ Gk, + G q f q q T h k, k, q T S G ] C ( ih) [ + ] C (0) C [ + C ( ih) ] (0) ε r q q / r σ *Assuption: an valu qual 0 σ varianc, C (τ) covarianc, T S r h ti duration of ti sgnt, h - ti intrval btwn two succssiv sapls, f th analysis rsolution. Both ships wr capabl of gnrating th voltag of 0 V, and aftr transforation V and 380 V as wll. Th asurnts wr don in thr ods: th ships wr standing still, anouvring and sa sailing. Th figur 3 prsnts frquncy analysis of th signal of noinal voltag of 0 V. Th asurnts wr takn whil th frry was sailing at sa. Th total haronic distortion THD did not cd 4 %. Figur 3. Ti wavfor signal and powr spctru dnsity of th signal of noinal voltag 0 V. Using th dsignd virtual dvic Flickr.vi, it was possibl to ak th analysis of th voltag changs in th switchboard that rsult in flickring of light luinanc. Th ai of flickr asurnt is to assss a valu prssing dirctly th dgr of irritation of huan bings causd by light

5 Vinna, AUSTRIA, 000, Sptbr 5-8 flickring. Thrfor, th voltag flickr is asurd with rspct to th snsitivity of a huan y. Th instantanous flickr snsation lvl S obtaind on th output of virtual instrunt [3] (includd in Signal Procssing and Analyzing Block of asurnt syst) was prsntd in Fig. 4. Th structur of a virtual flickrtr, corrsponding to th isting standards, is rsponsibl for prforing th asurnts, which ar basd on th siulation of th lap-y-brain bhaviour. Th absolut valu of th instantanous flickr snsation lvl is dividd by th corrsponding valu of th prcptibility thrshold in ordr to b prssd in trs of prcptibility units. On th ro-ro ship th short-tr flickr snsation lvl of th voltag did not cd th prcptibility thrshold. On th othr hand, th tporary considrabl valus of th instantanous lvl of flickr snsation wr obsrvd on th frry during ovrloads (Fig. 5). Th final statistical valuation calculats th short-tr flickr svrity lvl P st, which dirctly prsss th dgr of irritation, with P st p.u. aning th liit of disturbanc (thrshold of irritability). On Pst valu is basd on a short-tr obsrvation priod (tn inuts) and calculats as th root su of wightd prcntils of th instantanous flickr snsation lvl. Figur 4. Th instantanous flickr snsation lvl in th 0 V ntwork supplid by a shaft gnrator on a ro-ro ship. Figur 5. Th instantanous flickr snsation lvl in th ntwork of a frry ship during th bow thrustrs opration [4]. Th ship ntwork is charactrisd by th fluctuations in ffctiv valus of voltag and frquncy. This is causd by th work of non-cal rcivrs (charactrisd by suddn changs of grat powr), but also th ncssity of paralll work of at last two gnrating systs whil anouvring and rloading oprations whn thr is a gratr dand for lctrical powr. In rsult of th statistic analysis of th paratrs obtaind fro th asurnts on th frry whil anouvring in th ntwork of th noinal voltag 380 V it was possibl to dtrin th basic statistic paratrs for

6 Vinna, AUSTRIA, 000, Sptbr 5-8 rs voltag and frquncy (tab. 4). Th instantanous valus of rs voltag and frquncy wr obtain for ti fra qual 048 sapls during 40 in. ti obsrvation. Tabl 4. Th statistic proprtis of rs voltag and frquncy. Statistics rs voltag frquncy an 389,097 V 49,778 Hz standard dviation,337 V 0,044 Hz skwnss -,43 0 kurtosis 6,859 8,647 od 38,39 V 49,78 Th corrsponding th probability dnsity functions of assuing instantanous valus ar prsntd in Fig. 6. Figur 6. Th probability dnsity functions of rs voltag and frquncy in th ntwork of 380 V whil th frry was anouvring. 5 SUMMARY Th papr contains th plary rsults of intrfrnc analysis occurring in low voltag powr supply of ships, obtaind with th us of th prsntd syst. A copltly diffrnt probl is th dtaild inaccuracy valuation of th dtrind paratrs taking into account th asuring thod rrors and th rrors rsulting fro procssing (analysis) of th signal. This instrunt aftr slight odifications, spcially in th hardwar part, can b applid to asur and stiat signals, noiss, conductd and radiatd intrfrnc, which occur in various lctrical and lctronic dvics. REFERECES [] J.S. Bndat, A.,G. Pirsol, Rando dat: Analysis and asurnt procdurs, J,Wily,986. [] P.H. Sydnha, Handbook of Masurnt Scinc, Wily, w York, 983 [3] B. Pa³czyñska, L. Spiralski, Wirtualny syst do poiaru wskaÿników igotania œwiat³a urz¹dzñ oœwitlniowych zasilanych z sici niskigo napiê cia 50 Hz, in: Zszyty aukow Politchniki ódzkij, Elktryka nr 93, ódÿ 999, s (in Polish) [4] B. Pa³czyñska, T. Tarasiuk, Mthod of asurnt of voltag proprtis on bus bars of ship s ain switchboard tools and prliinary rsults, Polish Mariti Rsarch (accptd for publication) [5] DAQ ational Instrunts, PCI E Sris Usr Manual, 997. [6] LabVIEW Analysis VI Rfrnc Manual, ational Instrunts, 994 AUTORS: B. PA CZYÑSKA, Gdynia Mariti Acady, Dpartnt of Marin Radio Elctronics, Morska 83, 8-5 Gdynia, Poland, Phon , Fa E-ail: palbata@ws.gdynia.pl L. SPIRALSKI and A. KOCZAKOWSKA, Tchnical Univrsity of Gdañsk, ul. arutowicza /, Gdañsk, Poland, E-ail: kapsz@sunris.pg.gda.pl